This application claims the benefit of Japanese Applications No. 11-213812 now J.P. Publication No. 2001-039387 which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a pressure-proof optical apparatus for equipment used under a high-pressure environment. Herein, being xe2x80x9cunder the high-pressure environmentxe2x80x9d implies a deep ocean, or a high-pressure reaction chamber, etc. The xe2x80x9cequipment used under the high-pressure environmentxe2x80x9d may embrace categories of a deep ocean survey vehicle itself or the high-pressure reaction chamber itself, etc., which is used in a place where there is a large pressure difference between the external environment and the internal environment, or an imaging apparatus such as a camera used as a part of the above equipment, i.e., the deep ocean survey vehicle or the high-pressure reaction chamber receiving the large pressure difference between the external environment and the internal environment, or an imaging apparatus such as a camera exposed directly to the high-pressure environment as in the deep ocean or the high-pressure reaction chamber, etc. Further, the pressure-proof optical apparatus implies a pressure-proof window provided in the deep ocean survey vehicle or vessel, or the high-pressure reaction chamber itself used in the place where there is. the large pressure difference between the external-environment and the internal environment, or an imaging apparatus such as a camera used as a part of these apparatuses. The pressure-proof optical apparatus may further embrace a part of lens unit of the imaging apparatus such as a camera (pressure-proof underwater camera) exposed directly to the high-pressure environment as in the deep ocean, the high-pressure reaction chamber, etc.
2. Related Background Art
What has hitherto been known as a pressure-proof optical apparatus for equipment used under a high-pressure environment as in the case of a deep ocean survey vehicle, takes such a structure that an optical element which transmits the light is composed of plastic, or a glass, or quartz, or plastic properly cemented with glass.
A plastic window, because of the plastic itself exhibiting a small rigidity, is largely flexed or deformed when a high pressure is applied thereto. For preventing this large flexure, a thickness of the window is set large to a considerable degree. By contrast, the window composed of a glass or a transparent crystalline material such as quartz has a high rigidity and is therefore smaller in quantity of flexure than the plastic window but weak against a mechanical impact.
FIG. 1 shows the conventionally used pressure-proof window. This type of prior art pressure-proof windows, whether made of plastic or glass, inevitably become more or less flexural when the high pressure is applied. In the case of the window having a structure as shown in FIG. 1, a periphery of a window member 101 is fixed by a support member 102, and hence a central portion has a larger quantity of deformation due to the flexure than in the peripheral portion. If the window is thus flexed or deformed, the light coming from outside is refracted at an interface between the external region and the window member 101 with a difference in refractive index therebetween, and further refracted at an interface between the window member 10l and the internal region. This causes a problem in which an observed image of the outside is largely distorted. Especially when photographing the outside via the window, an image quality of the picture photographed is deteriorated. When trying to obtain a high-quality picture, the deterioration in image quantity turns out to be a serious problem.
It is a primary object to provide an pressure-proof optical apparatus capable of minimizing the deterioration of an observed image even when used under a high-pressure environment.
To accomplish the above object, according to one aspect of the present invention, a pressure-proof optical apparatus comprises an external side optical member disposed on the side of an external region, an internal side optical member disposed on the side of an internal region, a liquid filling portion formed by filling a space between the external side optical member and the internal side optical member with a liquid, and a liquid receding passageway for receding the liquid in the liquid filling portion if the external side optical member deforms. The external side optical member, the internal side optical member and the liquid are transparent with respect to the light that should be observed.
At least one of the: external side optical member and the internal side optical member may have refracting power.
The pressure-proof optical apparatus may further comprise a liquid receptacle, connected to the liquid receding passageway, for reserving the liquid receded, and a detection unit for detecting a quantity of the liquid reserved in the liquid receptacle in order to detect a pressure applied to the external side optical member.
A third optical member may be disposed on the side of at least one of the external region existing more outside than the external side optical member and the internal region existing more inside than the internal side optical member, and a space between the third optical member and the external or internal side optical member adjacent to the third optical member may be filled with the liquid.
According to another aspect of the present invention, a pressure-proof optical apparatus comprises a partition member for forming a window opened to an external region and an internal region which are connected liquid- and air-tightly to a partition wall for partitioning the external region in a high-pressure environment from the internal region in a normal-pressure environment, an external side optical member disposed liquid- and air-tightly with respect to the partition member on the side of the external region in an intra-window area of the partition member, an internal side optical member disposed liquid- and air-tightly with respect to the partition member on the side of the internal region in the intra-window area of the partition member, a liquid filling portion formed between the external side optical member and the internal side optical member, and filled with the liquid, and a liquid receding passageway for receding the liquid in the liquid filling portion if the external side optical member deforms. The external side optical member, the internal side optical member and the liquid are transparent with respect to the light that should be observed.
According to a further aspect of the present invention, a taking optical lens unit comprises a first optical system arranged at a front end of the lens unit and composed of a pressure-proof optical apparatus as set forth in any of claims of the present application and a second optical system arranged behind said first optical system and forming a taking optical system together with said first optical system.
In the last mentioned taking optical lens unit, said first optical system has an external side surface facing the external region, which surface is planer, concave or convex toward the external region.